This study examined the process of seizing power within the right-wing political forces, by focusing on the main variables that became the power base of Syngman Rhee from the liberation period to the period of the First Republic of Korea. Various variables had an effect on the seizure of power within the right-wing political forces. For this study, the mobilization of the masses and the anti-communist ideology that served as main variables were dealt with. In the process of seizing power, Syngman Rhee actively used the masses of right-wing public groups, the police, the military, and youth groups to compete for political power. In particular, Syngman Rhee strategically used the disposal of Japanese vested properties and free aid from the U.S. to create a sponsorship-sponsored structure centered on loyal and benevolent aides. He also implemented farmland reform to attract farmers as his base of support and took advantage of them as a means of his governance. Syngman Rhee also used anti-communist ideology based on 'Anti-Communist' and 'Northern Unification' as the ruling ideology. The Anti-Communist Ideology was not intended for North Korea, but rather internally-directed. Northern Unification Movement made the residents put together to strengthen their impenetrable anti-communist stance, forcing them to obey his own power who was a leader. Busan's political turmoil and the constitutional amendment, shown in the process of taking over power laid the foundation for Rhee Syng-man's long-term seizure of power until 1960. The reason why Rhee Syng-man was able to take power under a limited structural framework was that he made a success in utilizing two factors; public mobilization and anti-communist ideology.